Once the Atlantis began operating, armchair diving became Grand
Cayman's most popular spectator sport.

Since the mid-1980s, the sub has introduced thousands of passengers to the
marine life that lives a hundred feet underwater off George Town. However,
most people made the trip during daytime. For something new, ride the Atlantis
after dark.

After logging four daytime Atlantis dives, I'm curious to see how
the experience varies at night. The differences begin as soon as I climb into
the tube.

Instead of sunlight blasting through the numerous portholes, subdued fluorescent
lights illuminate the interior, making the Atlantis feel more like a submarine
than a floating mini-auditorium.

The show's already underway. Baby tarpon of only 15-20 pounds--looking like
hundred-pound behemoths thanks to the porthole distortion--flit back and forth
in the bright underwater lights like insects as they search for small fish
blinded by the glare.

It's hard to tell the exact number but I estimate between 15-20 of the dashing,
silver-scaled fish are schooling around the sub. They end up accompanying
us, their mobile feeding station, throughout the voyage.

Reaching bottom, we spot a seemingly dinner-plate sized Caribbean king crab
scuttling through the corals. The waving antennas of several lobsters also
give themselves away. Spotting movement like this is the key to spotting animals
at night.

Suddenly our narrator becomes unusually excited as we encounter one, then
two, nurse sharks cruising the reef. When we spot a third shark, he babbles
like we've all just hit the lottery.

To him, we have. Encountering sharks at night is extremely rare, he assures
us. In fact, he says these are the first he's ever seen.

Ironically, although the sub's lights perfectly display the varied colors
of the corals and sponges, the reef is secondary, only a backdrop, as we increase
our creature count.

We spot 5 more lobster, another Caribbean king crab and even an octopus on
the edge of the Cayman wall.

The evening's highlight comes at the end, when both interior and exterior
lights are turned off and our portholes reveal something unexpected: a huge
swarm of underwater fireflies.

It's the bioluminescence which has been there all along but overwhelmed by
our lights. I would happily watch this light show for hours but we're given
only a few minutes. The next group of passengers awaits.